P6 a retrospective study outcome in patients with Argentine haemorrhagic fever was associated with the amount of neutralising antibodies against Junin virus present in the transfused units of immune plasma. Low doses of neutralising antibodies were associated with higher mortality. A prospective study gave comparable results. A dose of no less than 3000 therapeutic units of neutralising antibodies per kg body weight is recommended. It is also suggested that the lack of effectiveness of immune plasma in the treatment of other viral haemorrhagic fevers, such as Lassa fever and Crimean-Congo haemorrhagic fever, may be due to a low dose of the specific neutralising antibodies.